DataFormat.Error: We cannot convert the specified value to the specified type.

Anonymous & Bjoern.

I have this problem getting data from a custom object in a SalesForce (SF) table. 

Here's how I solved my issue - Hope this helps you:

1) Query to get just the column names, so i can pass that to a function that finds the offending column with the data type that PowerQuery (PQ) can't deal with.

let
    Source = Salesforce.Data(),
    MyTable_c = Source{[Name="MyTable_c"]}[Data],
    LSTHeaders = Table.ColumnNames(MyTable_c),
    LST2Table = Table.FromList(LSTHeaders, Splitter.SplitByNothing(), null, null, ExtraValues.Error)
in
    LST2Table

2) Write a function to pass each column (i had 175) and get back just the first row - using "TRY" - this told me what column error'ed out.

let fnMCRColName = (MCRColName as text) => 

let
    Source = Salesforce.Data(),
    Source2 = Source{[Name="MyTable__c"]}[Data],
    LSTHeaders = Table.ColumnNames(Source2),
    FinalTable = Table.SelectColumns(
            Source2,
            {
                 MCRColName
            }
    ),
    FirstRow = Table.First(FinalTable)
in
    FirstRow
in
    fnMCRColName

3.

Add column to the first query results using the TRY function:  Try fnLookup(querylist_colnames)

4.

Expand the custome record - you should see something like this:

5. You can see I have a GeoLocation_c column in my customer SF ojbect that PQ probably doesn't like.  I've tried casting it to TEXT, but that doesn't work. 

I'm going to update my query to remove that column

Eric.